There are certain automobile automatic transmissions which are manufactured with a thrust-washer encircling the oil pump stator shaft which protrudes through, and is an integral part of, the pump cover in the oil pump assembly. The thrust-washer is located on the pump stator shaft on the rear side of the pump cover which is the side distal (rearward) from the engine. The stator shaft on the side of the pump cover on said distal side is several inches in length and is provided with the said thrust-washer followed by oil seal rings located sequentially in separate parallel radial grooves encircling the stator. Following that is a bearing surface encircling the stator and following that there are more oil seal rings. Onto this stator shaft the direct clutch drum is positioned so that the stator shaft, carrying the oil seal rings and bearing surface, is snugly enclosed within the inner circumference of the direct clutch drum. The inner circumference of the direct clutch drum (which we shall also call a "rotor") has a surface which is prepared as a bearing surface and which aligns with the bearing surface which encircles the stator shaft. When assembled, the frontal portion of the direct clutch drum, which is cylindrical in appearance and which protrudes through the main body of the direct clutch drum, is rotatable around the stator shaft and the frictional forces are carried radially by the bearing and laterally by the thrust-washer.
Since the direct clutch drum is subjected to high rpm speeds, it is necessary that there be a steady flow of oil to the bearing surfaces, to the surfaces in contact with the thrust-washer, to the oil seal rings and to the other parts which form the remainder of the oil pump assembly and the clutch drum. The oil is supplied by the oil pump assembly and is forced at high pressure through channels within the walls of the stator shaft and through small holes or ports to the areas between the stator shaft and the rotor.
A common cause of transmission failure is the wearing of the thrust-washer which allows lateral "play" or looseness in the fast turning rotor. This "play" becomes a "wobble" and the customary bearing surface is rapidly worn away. This wobbling of the clutch drum also causes rapid wearing of the oil seal rings and also causes excessive wear of the stator shaft in the area of the thrust-washer. Wearing of the inside periphery of the rotor can also occur. This wearing away causes loss of oil pressure, needed to operate the clutches, and this results in overheatng. The overheated oil tends to vaporize and lose its ability to lubricate and the oil rings often become "heat-welded" to the stator, thus causing excessive wear, and even gouging, of the inner circumference of the rotor. Furthermore, the loss of oil pressure and the overheatng causes damage to other parts of the transmission. The cost of overhauling such a damaged transmission and replacing the damaged parts often runs into the hundreds of dollars.
Various attempts have been made by manufacturers of the transmissions to improve the wear rate of the thrust-washers, and have even tried using "needle-washers" which are assembled much like small bar-bearings positioned in a plane parallel to, and between, two flat washer surfaces. Repair kits have been sold which employ "shims" to take up the slack in the thrust direction by supplementing the thickness of the thrust-washer. These attempts to improve the wear rate in the area of the thrust washer have been, in the long run, substantially ineffective.
The transmissions which are improved by the present invention are, e.g., of the type known as Turbo Hydra-matic 250 and 350. Also Ford-o-Matic C-4 and other similar transmissions while differing slightly in the manner in which the stator and the rotor are designed, still suffer from essentially the same kind of wear at a similar thrust washer, and are also improved by applying the concept and features of the present invention.
It is an object of the present invention to improve the wear-rate of the automatic transmissions known as Turbo Hydra-Matic 250 and 350 and Ford-o-matic C-4 and others which have similar stator shaft/rotor assemblies.
It is another object to improve the wear-rate at the union of the stator shaft and rotor of said transmissions.
Another object is to provide a radial-bushing around the stator shaft on which the rotor turns and which is juxtapositioned with the thrust-washer; the radial bushing supplements the existing bearing on which the rotor turns.
Still another object is to improve the manufacture of said transmissions by modifying the stator to receive a radial-bushing encircling its frontal outer circumference, juxtapositioned with the thrust-washer when the transmission is assembled.
Yet another object is to provide a combination thrust-washer and radial-bushing for use with modified existing stator shaft/rotor assemblies.
A still further object is to provide tooling specially designed to allow easy modification of existing rotor designs so as to enable the existing rotor designs to receive the radial-bushing of the present invention.
These and other objects are attained by the present invention which is described and illustrated herein.